package 华为机试8月23日;

import java.util.Scanner;

public class 华为第一题 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String s = sc.nextLine();
            System.out.println(func(s));
        }
        sc.close();
    }

    private static String func(String s) {
        if (s.length() > 20)
            return "ERROR!";
        if (s.replaceAll("[^0-9a-zA-Z]+", "").length() != s.length())
            return "ERROR!";
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i += 2) {
            sb.append(String.valueOf(s.charAt(i)));
        }
        return sb.toString();
    }
}
